1. Field of the Invention
The present invention relates to an automobile heating, ventilation, and air conditioning unit usually abbreviated to "HVAC unit" or to "HVAC module", and specifically to a one-box type automobile HVAC unit capable of being automatically controlled through either an electronic control unit (ECU) or an electronic control module (ECM), or a body control module or a body computer module (BCM).
2. Description of the Prior Art
In recent years, there have been proposed and developed various automobile heating, ventilation, and air conditioning (HVAC) systems whose automatic control can be achieved by an ECU/ECM coordinating all engine functions such as the fuel injection and ignition system or a BCM handling the functions of controlling such items as an electronic comfort control system or an electronic climate control system. A typical HVAC unit contained in the electronic climate control system (ECC system), has at least a heating, ventilation, and air conditioning (HVAC) case, an evaporator core assembly, and a heater core assembly. The HVAC case defines therein an air mix chamber in which the evaporator core air (cold air) and the heater core air (warm air) are properly blended or mixed, depending on the degree of air-mix-door opening. The air mix door is generally constructed as a pivotable or swingable air mix door flap. The amounts of blended air or conditioned air flowing through the vent outlet, the defroster outlet, and the foot vent outlet are adjusted by regulating the position of the respective control doors. The HVAC case has the vent, defroster, and foot-vent outlets above the air mix chamber. In order to attain the discharged-air amount regulation or the discharge mode control on the rear passenger compartment, the conventional HVAC unit requires a rear vent outlet on the upper wall of the HVAC case in addition to the vent outlet containing a center vent, and side vents, and also requires an additional control door for opening and closing the rear vent outlet. Additionally, a rear vent duct must be connected to the rear vent outlet to feed the conditioned air (temperature-blended air) to the rear passenger compartment. Usually, the rear vent duct and the foot vent duct are fitted to the outside wall of the HVAC case so that the rear vent duct extends downwards from the rear vent outlet along the HVAC case outside wall and so that the foot vent duct extends downwards from the foot vent outlet along the outside wall of the HVAC case to direct conditioned air toward the floor outlet. The HVAC unit is thus large-sized and its structure is complicated. This increases the number of parts of the HVAC unit. When installing a prior art HVAC unit as set out above within the vehicle passenger compartment, it is necessary to mount the HVAC unit having the foot-vent and rear vent ducts significantly projected from the HVAC-case outer wall on the vehicle with caution without interfering with any functional component parts incorporated on or in the vehicle instrument panel, such as the instrument-panel cluster assembly, the wiring harness assembly, the voice/chime module, or the like. Projected duct portions may disturb easy installation of the HVAC unit within the passenger compartment. Also, in the conventional HVAC unit, air properly conditioned or temperature-adjusted within the air mix chamber is generally discharged or blown into the rear passenger compartment through the rear vent outlets, as well as into the front passenger compartment through the front vent outlets (containing center, side vents). Therefore, the conventional HVAC unit having the ventilation-duct and discharge-outlet structure, cannot make independent temperature adjustments on the front and rear passenger compartments. It is desired to make independent temperature adjustments on the front and rear sides of the vehicle with a simple HVAC unit being compact in size.